Automatic conveyers are used in industry, commerce and service installations such as the Post Office to handle the transportation of the loads incident to the installation. These conveyers may be hundreds or thousands of feet in length and include cross or connecting conveyers for storage, processing, sorting and other operations. The conveyers may run continuously, such as the main trunk conveyer, and the cross or connecting conveyers may optionally run or not run. All the incoming loads are placed on the main trunk conveyer and borne to the other conveyers. Also processed loads from the cross or connecting conveyers may be returned to the main trunk conveyer for shipment out of the installation. The loads traveling on the main trunk conveyer thus have to be stopped while processed loads from the cross or connecting conveyers are loaded back on to the main trunk conveyer. Many other reasons may necessitate the stopping of loads traveling on the main trunk conveyer such as no available capacity to receive the load on the cross or connecting conveyers, breakdown of equipment, spillage, clean-up, maintainance, shutdown of daily operations, selective stopping of particular loads, etc.
Stop devices are used on the trunk and connecting conveyers to stop loads as desired. These devices are automatic or semi-automatic and respond to signals which may be automatic or semi-automatic. The stop devices of the prior art employ large expensive solenoids or air cylinders to stop the loads with the solenoids or air cylinders bearing the inertia and momentum forces of heavy loads traveling rapidly on the conveyers. If the solenoids and air cylinders were not large and powerful, the forces of the rapidly traveling heavy loads would push the stop positioned by the solenoid or air cylinder out of the way and keep on traveling. In some instances heavy springs are used to place the stop in position and here the springs must be strong enough to withstand the forces of the rapidly traveling loads. To move the stop out of the way against the heavy spring, a large powerful, expensive solenoid or air cylinder is needed to overcome the heavy spring. Heavier electrical wiring and larger air lines are needed to operate the large power means than the ones used on the rest of the control system. Also greater EMF and air supply is required increasing the expense of installation and operation. The stop devices of the prior art are thus large, additionally powered, and expensive.